1. Technical Field
The present technical field relates to an ink-jet apparatus.
2. Description of the Related Art
An ink-jet apparatus has a head capable of applying a required amount of ink to an object at given timing in response to an input signal. Especially, a piezoelectric ink-jet apparatus has been positively developed because various kinds of ink can be applied while being controlled with high precision.
In general, the piezoelectric ink-jet apparatus includes an ink supply flow path, an ink flow path connected to the ink supply flow path and having a nozzle, and a piezoelectric element to apply a pressure to ink supplied into the ink flow path. Thus, mechanical strain is generated in the piezoelectric element by applying a drive voltage to the piezoelectric element, and the ink is ejected from the nozzle by applying a pressure to the ink in the ink flow path. In addition, a space in which the ink is collected is called an ink chamber or a pressure chamber provided in the ink flow path.
For example, a configuration of a representative ink-jet apparatus is provided such that the piezoelectric element is arranged on a wall surface of the pressure chamber provided upstream of an ejection hole, and the wall surface of the pressure chamber is pressed by driving the piezoelectric element and a pressure is applied to the ink filled in the pressure chamber, whereby the ink is ejected from the ejection hole (refer to FIG. 1 of Unexamined Japanese Patent Publication No. 2001-121693. In addition, FIG. 1 of Unexamined Japanese Patent Publication No. 60-217160 discloses an ink-jet head provided such that electrostrictive element 4 is arranged in a part of ink supply path 11, and ink is ejected from nozzle 9. In addition, ink-jet apparatuses are disclosed in Unexamined Japanese Patent Publication No. 2007-175921, Japanese Translation of PCT Publication No. 2006-510506, Unexamined Japanese Patent Publication No. 2004-259865, Unexamined Japanese Patent Publication No. 2001-347660, U.S. Patent Publication No. 2006/0227179, U.S. Pat. No. 6,450,627, U.S. Pat. No. 7,157,837, and U.S. Pat. No. 7,111,927.
However, an idea of circulating ink in the ink-jet apparatus is not disclosed in the above Unexamined Japanese Patent Publication No. 2001-121693 and Unexamined Japanese Patent Publication No. 60-217160 at all. That is, the ink-jet apparatuses disclosed in Unexamined Japanese Patent Publication No. 2001-121693 and Unexamined Japanese Patent Publication No. 60-217160 are simply based on a technique to eject liquid held in the pressure chamber (ink supply path) from a nozzle hole by driving the piezoelectric element, and they are not based on a technique to provide an ink supply flow path and an ink discharge flow path and circulate ink therebetween.
Especially, in the configuration of the ink-jet apparatus in Unexamined Japanese Patent Publication No. 2001-121693, the ink could stagnate in a corner part of the pressure chamber or the nozzle hole, and the nozzle hole could be clogged. Thus, in a case where the ink has high viscosity, it is hard to eject the ink from the nozzle hole. In addition, as for the ink-jet head in Unexamined Japanese Patent Publication No. 60-217160, a pressure generated by driving electrostrictive element 4 and applied to the ink flowing in ink supply path 11 is dispersed to the upstream side of electrostrictive element 4 (in a direction opposite to nozzle 9), so that it is difficult to eject the ink strongly toward nozzle 9.